The invention relates generally to a lubrication of a gearbox and more particularly, to a system of lubricating a fluid turbine gearbox during idling or loss of electric grid.
In general, a wind turbine gearbox is supplied with oil for lubricating the bearings and meshing gears of the gearbox by a conventionally operated electrical pump. Such pumps may be efficiently operated for lubrication during on grid conditions, thereby, making use of the electric power generated from the turbine. But, during the time of no electric grid or idling, the conventional electrically operated pump cannot be used to supply the oil to the various components of the gearbox including the bearings and meshing gears unless a backup power source is available. The use of an auxiliary power source leads to additional costs and is not generally preferable in view of high cost of operation of the lubrication system. Some other typical wind turbine gearbox lubrication systems include a mechanically coupled geared pump for providing lubricating oil to the gearbox. Such pumps are attached to a gearbox shaft on the blade side of the wind turbine or generator side of the wind turbine. However, during emergency conditions such as failure of the mechanically coupled geared pump or maintenance of the electrically operated pump, supply of lubricating oil to the gearbox may not be available. This causes excessive heating of the components of the gearbox and may lead to failure due to increased stresses. Although wind turbine gearboxes are described herein for purposes of illustration, such embodiments are useful for other types of fluid turbines such as marine hydrokinetic energy devices, for example.
Accordingly, there exists a need for an efficient lubrication system for lubricating a fluid turbine gearbox during loss of electric grid, idling or any other emergency conditions.